From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1DF6B4963A; Mon, 8 Jul 2024 19:00:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720465240; cv=none; b=dQukETaHUwdu7YNOpIAmQs1ueSHyIBYS9BMHepAoM2IrAljqC7Uvh9DQxPzPJ0RFU3KdMkfvHHe/27OjfwwCDPb4wkEs2vXhCeF4Kd1EblcRDdXY19vyod8gv6hmLrH3JxwOo7mtBloaWFwarSnIzisuGqK/ZgMZN/IS6kbXVh4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720465240; c=relaxed/simple; bh=/KJSuRj9+leevqGL33u7xwNFS5JRZBNfnt+9fLhdWYA=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=mTJw2M+6z+4vU2DzhwzUvK9nd2W40w4YqJyTjIwoYmehKnsxo9cw/3n3I2GED7OjnHLH2Zs6X2GGM08Dip1irB/TYpvezQ5auOG5I7H0CQMagCe6x220XA6yGMCqznyiHAceuLRAAS6SVMsRxsAFt4zvxnwtHBwPJ6i1XXQK+xo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=hj80xRBb; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="hj80xRBb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5A4BDC116B1; Mon, 8 Jul 2024 19:00:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1720465239; bh=/KJSuRj9+leevqGL33u7xwNFS5JRZBNfnt+9fLhdWYA=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=hj80xRBbmLhzA8qcAJmBP/185o0WBmfsVtkHngJWOBRa2U2Ku68jRjMWefZa9+ySB wjkiked2916GS2b5GtxyakCniHd2VrjnVDavBrm7exuKFt7h/VpBO8UxwWishJl6aM RTo0tLfG85HSt8TeYHzvjprZ2SiOZ3OyLZPka2HarhwMb4OnpLEjOSTDRxYxsjOTKY rekkZ7nIOGIFtWN2gS1UEZfrYinVb05byhi26qA3hOmkxCxLYBNnr6CWBe5Kwas42d 3mcKENB1pWoDrUBBnLz1R1StqMJf42E5JdV0cpGXXEuyS1AC6xzLjfbSQ0LZy6Wu5L //PODtHLOeQ4w== Message-ID: <0cedef23cf87d598b2c03e850262ac55bca9e792.camel@kernel.org> Subject: Re: [PATCH v4 6/9] xfs: switch to multigrain timestamps From: Jeff Layton To: "Darrick J. Wong" Cc: Alexander Viro , Christian Brauner , Jan Kara , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Chandan Babu R , Theodore Ts'o , Andreas Dilger , Chris Mason , Josef Bacik , David Sterba , Hugh Dickins , Andrew Morton , Jonathan Corbet , Dave Chinner , Andi Kleen , Christoph Hellwig , Uros Bizjak , Kent Overstreet , kernel-team@fb.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-ext4@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-mm@kvack.org, linux-nfs@vger.kernel.org, linux-doc@vger.kernel.org Date: Mon, 08 Jul 2024 15:00:36 -0400 In-Reply-To: <28e7a6c193674f2aa41ab1eec9bb8747ddba1a4c.camel@kernel.org> References: <20240708-mgtime-v4-0-a0f3c6fb57f3@kernel.org> <20240708-mgtime-v4-6-a0f3c6fb57f3@kernel.org> <20240708184739.GP612460@frogsfrogsfrogs> <28e7a6c193674f2aa41ab1eec9bb8747ddba1a4c.camel@kernel.org> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; 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text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.52.2 (3.52.2-1.fc40app2) Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Mon, 2024-07-08 at 14:51 -0400, Jeff Layton wrote: > On Mon, 2024-07-08 at 11:47 -0700, Darrick J. Wong wrote: > > On Mon, Jul 08, 2024 at 11:53:39AM -0400, Jeff Layton wrote: > > > Enable multigrain timestamps, which should ensure that there is an > > > apparent change to the timestamp whenever it has been written after > > > being actively observed via getattr. > > >=20 > > > Also, anytime the mtime changes, the ctime must also change, and thos= e > > > are now the only two options for xfs_trans_ichgtime. Have that functi= on > > > unconditionally bump the ctime, and ASSERT that XFS_ICHGTIME_CHG is > > > always set. > > >=20 > > > Finally, stop setting STATX_CHANGE_COOKIE in getattr, since the ctime > > > should give us better semantics now. > > >=20 > > > Signed-off-by: Jeff Layton > > > --- > > > fs/xfs/libxfs/xfs_trans_inode.c | 6 +++--- > > > fs/xfs/xfs_iops.c | 10 +++------- > > > fs/xfs/xfs_super.c | 2 +- > > > 3 files changed, 7 insertions(+), 11 deletions(-) > > >=20 > > > diff --git a/fs/xfs/libxfs/xfs_trans_inode.c b/fs/xfs/libxfs/xfs_tran= s_inode.c > > > index 69fc5b981352..1f3639bbf5f0 100644 > > > --- a/fs/xfs/libxfs/xfs_trans_inode.c > > > +++ b/fs/xfs/libxfs/xfs_trans_inode.c > > > @@ -62,12 +62,12 @@ xfs_trans_ichgtime( > > > ASSERT(tp); > > > xfs_assert_ilocked(ip, XFS_ILOCK_EXCL); > > > =20 > > > - tv =3D current_time(inode); > > > + /* If the mtime changes, then ctime must also change */ > > > + ASSERT(flags & XFS_ICHGTIME_CHG); > > > =20 > > > + tv =3D inode_set_ctime_current(inode); > > > if (flags & XFS_ICHGTIME_MOD) > > > inode_set_mtime_to_ts(inode, tv); > > > - if (flags & XFS_ICHGTIME_CHG) > > > - inode_set_ctime_to_ts(inode, tv); > > > if (flags & XFS_ICHGTIME_CREATE) > > > ip->i_crtime =3D tv; > > > } > > > diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c > > > index a00dcbc77e12..d25872f818fa 100644 > > > --- a/fs/xfs/xfs_iops.c > > > +++ b/fs/xfs/xfs_iops.c > > > @@ -592,8 +592,9 @@ xfs_vn_getattr( > > > stat->gid =3D vfsgid_into_kgid(vfsgid); > > > stat->ino =3D ip->i_ino; > > > stat->atime =3D inode_get_atime(inode); > > > - stat->mtime =3D inode_get_mtime(inode); > > > - stat->ctime =3D inode_get_ctime(inode); > > > + > > > + fill_mg_cmtime(stat, request_mask, inode); > >=20 > > Sooo... for setting up a commit-range operation[1], XFS_IOC_START_COMMI= T > > could populate its freshness data by calling: > >=20 > > struct kstat dummy; > >=20 > > fill_mg_ctime(&dummy, STATX_CTIME | STATX_MTIME, inode); > >=20 > > and then using dummy.[cm]time to populate the freshness data that it > > gives to userspace, right? Having set QUERIED, a write to the file > > immediately afterwards will cause a (tiny) increase in ctime_nsec which > > will cause the XFS_IOC_COMMIT_RANGE to reject the commit[2]. Right? > >=20 >=20 > Yes. Once you call fill_mg_ctime, the first write after that point > should cause the kernel to ensure that there is a distinct change in > the ctime. >=20 > IOW, I think this should alleviate the concerns I had before with using > timestamps with the XFS_IOC_COMMIT_RANGE interface. >=20 >=20 Oh, and to be clear, if you're _only_ worried about changes to the contents of the file (and not the metadata), you should be able to do this instead: fill_mg_ctime(&dummy, STATX_MTIME, inode); ...and that should avoid false positives from metadata-only changes. Querying only the mtime still causes the QUERIED flag to be set, and the kernel to give you distinct timestamps. > > --D > >=20 > > [1] https://lore.kernel.org/linux-xfs/20240227174649.GL6184@frogsfrogsf= rogs/ > > [2] https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.gi= t/commit/?h=3Datomic-file-commits&id=3D0520d89c2698874c1f56ddf52ec4b8a3595b= aa14 > >=20 > > > + > > > stat->blocks =3D XFS_FSB_TO_BB(mp, ip->i_nblocks + ip->i_delayed_bl= ks); > > > =20 > > > if (xfs_has_v3inodes(mp)) { > > > @@ -603,11 +604,6 @@ xfs_vn_getattr( > > > } > > > } > > > =20 > > > - if ((request_mask & STATX_CHANGE_COOKIE) && IS_I_VERSION(inode)) { > > > - stat->change_cookie =3D inode_query_iversion(inode); > > > - stat->result_mask |=3D STATX_CHANGE_COOKIE; > > > - } > > > - > > > /* > > > * Note: If you add another clause to set an attribute flag, please > > > * update attributes_mask below. > > > diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c > > > index 27e9f749c4c7..210481b03fdb 100644 > > > --- a/fs/xfs/xfs_super.c > > > +++ b/fs/xfs/xfs_super.c > > > @@ -2052,7 +2052,7 @@ static struct file_system_type xfs_fs_type =3D = { > > > .init_fs_context =3D xfs_init_fs_context, > > > .parameters =3D xfs_fs_parameters, > > > .kill_sb =3D xfs_kill_sb, > > > - .fs_flags =3D FS_REQUIRES_DEV | FS_ALLOW_IDMAP, > > > + .fs_flags =3D FS_REQUIRES_DEV | FS_ALLOW_IDMAP | FS_MGTIME, > > > }; > > > MODULE_ALIAS_FS("xfs"); > > > =20 > > >=20 > > > --=20 > > > 2.45.2 > > >=20 > > >=20 >=20 --=20 Jeff Layton